Code example for function/delegate as template argument ?

[Basile B. via Digitalmars-d-learn]

On Wednesday, 4 May 2016 at 06:21:36 UTC, chmike wrote:
> Hello,
>
> I failed to find some code example for a template class/struct 
> that accept a function/delegate as template argument. All 
> examples I could find use simple value types like int or double.
>
>
> I piggy bag another question. Defining a function/delegate as 
> function argument is shown in examples. What I could not find 
> is how would I pass an object instance with a method to call ? 
> In C++ we use std::bind. How do we do that in D ?

Hello, you can use an alias this to pass a lmbda (or a delegate):

----
module runnable;

import std.stdio;

struct Foo(alias fun)
{
     this(string text)
     {
         fun(text);
     }
}

void main(string[] args)
{
     alias fun = (a) => a.writeln;
     auto foo = Foo!fun("hello");
}
----

I suppose that a constraint would be welcome be that's not the 
point here.